1. Field of the Invention
The present invention relates to sport boots, especially gliding sports, such as cross-country skiing or skating, or other sports, such as biking, in which the boot must be attached to the sport article while preserving a possibility of foot movement during the practice of the sport, or is independent thereof, for example, when walking.
2. Description of the Background and Material Information
In the aforementioned sports, and especially in cross-country skiing, various methods of fastening the boot to the sport article have been investigated.
Thus, the conventional binding method consists in attaching the boot to the cross-country ski by means of a stirrup cooperating with a front overlapping part of the sole and pressing this part against the cross-country ski.
Such a binding method prevents the complete movement of the foot since the foot is attached to an entire front part. To overcome this drawback, various systems have been proposed to articulate the boot on the cross-country ski around an axle attached transversely to the boot.
Different positions and anchoring methods of this axle at the front of the boot, at the level of the metatarsal zones, by means of inserts, etc., have been tested with a more or less degree of satisfaction.
The problem, in fact, is that a compromise must be found between two completely contradictory requirements, namely:
a maximum movement of the foot, necessary for obtaining a substantial impulse or a wide stride, depending on the sport practiced; PA1 an optimum control and steering of the gliding member or sport article which, in theory, can only be obtained through a permanent "contact" between the foot and the former, and therefore it is not compatible with a movement of the foot; PA1 a sufficient anchoring of the insert or of the articulation axle in the sole so as to keep the axle or insert from being pulled out when practicing the sport.
This problem was partially resolved in the document FR 2 739 788, which provides an assembly of a boot and a device for binding a boot to a sport article, in which the boot has two anchoring means constituted by transverse axles arranged, one at the front of the boot, and the other substantially in the area of the metatarsophalangeal articulation zone, and in which the binding device is provided so as to allow the rotation of the boot around the first anchoring axle and to exert a constant elastic return on the second anchoring axle in the direction of the sport article.
Thus, providing means for the elastic return of the boot towards the sport article, not at the front of the boot as in currently known devices, but at the rear of the binding means of the boot, allows controlling the boot with respect to the gliding member even when the boot is raised.
Such a boot/binding system therefore allows reconciling the problems of raising and control/steering of the boot with respect to the sport article, and therefore allows, in principle, an optimum movement of the foot.
However, such a movement of the foot, especially during the final pivoting phase around the metatarsophalangeal articulation, can only be obtained with a boot that is particularly flexible in the entire front zone of the boot.
Such a requirement for flexibility is difficult to reconcile with an anchoring of rotational axles, connecting means, or inserts arranged specifically in this zone.
Indeed, the anchoring techniques known, for example, in documents FR 2 533 421, WO 88/05271, and FR 2 645 038, all use an insert, whether of hard plastic or metallic materials, extending along a substantially horizontal plane in the longitudinal direction of the sole and stiffening the latter proportionately.
In the case of U.S. Pat. No. 4,872,272, the articulation axle is constituted by the transverse arm of a U-shaped buckle, whose lateral arms also extend deeply inside the sole in the longitudinal direction and therefore prevent any flexion at the level of the lateral arms. The constraint of a correct anchoring of the insert or rotational axle is greater especially as the material constituting the sole is soft, and the forces exerted on the insert or axle during the practice of the sport are substantial.